We continue the in-depth analysis of the machinery dedicated to hot forging, through the family of presses.
Hydraulic, eccentric and knuckle joint presses
Depending on how it works, the press can fall into three distinct groups: hydraulic, eccentric and knuckle joint.
The hydraulic presses, using Pascal’s law, operate the ram, between the guide columns arranged in a V shape, by means of a hydraulic cylinder, powered by a hydraulic motor.
Compared to power hammers, hydraulic presses:
- have greater precision, as they are less influenced by external factors, such as vibrations;
- are slower, but for this reason the springback in the components is minimal;
- are unable to raise the temperature of the components and, for this reason, they are less suitable for obtaining low thickness components.
The eccentric presses operate the ram by means of an eccentric shaft with two supports or slider-crank, powered by an electric motor.
The eccentric presses can be muzzle, direct transmission, or delayed, where the power is amplified by the use of reduction gears.
Compared to hydraulic presses, they are more “robust” and require less maintenance.
There is a particular “front” eccentric press, called swan neck, which, due to its C-shaped structure, allows working on the three free sides (useful for example in sheet metal processing).
Knuckle joint presses
Finally, the knuckle joint presses, also powered by an electric motor, operate the ram by means of a system of levers. This transform the circular motion into alternating rectilinear motion.
As with hydraulic presses, due to the time required for the reversal of motion, the springback in the components is minimal.
Compared to hydraulic and eccentric presses, the force during the stroke is more constant, and so is the precision.